The present invention provides a method of treating acute and chronic myeloid leukemia (AML & CML) and lymphoid leukemia, said method comprising administering a pharmaceutical composition comprising pharmaceutically effective amount of chlorogenic acid (CA) and 3-o-p-Coumaryl quinic acid (PCQ) isolated from any plant parts of Piper betel or any other source, both individually or in a synergistic combination optionally along with pharmaceutically acceptable additives.